At present, stereo encoding methods mainly include coding methods, such as strength stereo, BBC (Binaual Cure Coding) and PS (Parametric-Stereo coding). In communications scenarios of medium and high code rates, the common encoding method is to extract the interchannel (for example, left and right channels) level difference (InterChannel Level Difference, ILD) (also known as CLD) and interchannel phase difference (InterChannel Phase Difference, IPD). In certain cases, the interrelation parameters of two channels and phase difference parameters between down-mixed signals and one of the channels may also be extracted. The parameters served as side information are encoded and sent to a decoding end, so as to restore a stereo signal. However, in communication scenarios with low code rates, ILD and IPD cannot be transmitted simultaneously. The ILD is required to be transmitted with priority. The ILD is encoded and sent to the decoding end to restore the stereo signal.
According to the preceding stereo encoding method, the corresponding stereo decoding method is as follows: extracting a monophonic bit signal from a code stream, obtaining a monophonic signal after decoding, and obtaining a monophonic frequency-domain signal after performing time-frequency conversion for the monophonic signal; in the scenarios of medium and high code rates, extracting an ILD and IPD from the code stream, and obtain a left channel frequency-domain signal and a right channel frequency-domain signal according to the monophonic frequency-domain signal and ILD and IPD; in the scenarios of low code rates, extracting an ILD from the code stream, and obtain a left channel frequency-domain signal and a right channel frequency-domain signal according to the monophonic frequency-domain signal and ILD; and obtaining a left channel signal and a right channel signal after performing frequency-time conversion for the left channel frequency-domain signal and right channel frequency-domain signal, respectively.
The stereo decoding method in the communication scenario with low code rates refers to only the ILD to achieve the sound field effect. That is, the signal obtained by using the decoding method includes only the energy value information between two channels of signals, thereby causing poor effects of the stereo sound field of the left channel signal and right channel signal.